libgo patch committed: Commit final version of pkg-config support

[Ian Lance Taylor]

This patch updates gccgo to the final version of the gccgo pkg-config
support committed to the gc repository.  The patch to gc is
https://golang.org/cl/18790, by Michael Hudson-Doyle.  This fixes
https://golang.org/issue/11739.  Bootstrapped and ran Go testsuite on
x86_64-pc-linux-gnu.  Committed to mainline.

I will commit this to the GCC 6 branch when that is open for bug fixes.

Ian
-------------- next part --------------
Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE	(revision 234958)
+++ gcc/go/gofrontend/MERGE	(working copy)
@@ -1,4 +1,4 @@
-ff29ea8e4e69eb94958aef4388da09a61b2b52b6
+97b358f525584e45fa2e3d83fc7d3a091900927a
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/cmd/go/build.go
===================================================================
--- libgo/go/cmd/go/build.go	(revision 234304)
+++ libgo/go/cmd/go/build.go	(working copy)
@@ -2647,9 +2647,18 @@ func (tools gccgoToolchain) ld(b *builde
 		if err != nil {
 			return err
 		}
+		const ldflagsPrefix = "_CGO_LDFLAGS="
 		for _, line := range strings.Split(string(flags), "\n") {
-			if strings.HasPrefix(line, "_CGO_LDFLAGS=") {
-				cgoldflags = append(cgoldflags, strings.Fields(line[13:])...)
+			if strings.HasPrefix(line, ldflagsPrefix) {
+				newFlags := strings.Fields(line[len(ldflagsPrefix):])
+				for _, flag := range newFlags {
+					// Every _cgo_flags file has -g and -O2 in _CGO_LDFLAGS
+					// but they don't mean anything to the linker so filter
+					// them out.
+					if flag != "-g" && !strings.HasPrefix(flag, "-O") {
+						cgoldflags = append(cgoldflags, flag)
+					}
+				}
 			}
 		}
 		return nil